This invention relates to turbine blade technology and, more specifically, to a replacement turbine blade having a discrete tip cap configuration that facilitates manufacture in a manner that increases blade life.
Some turbine components, such as rotor blades, have required replacement after one service interval (for example, three years) because of the inability to repair the component. For some turbine blades, the limiting factor is the integral “cast-in” tip cap design of the blades which requires that the core support used in casting the blade be internally supported by many small platinum pins that extend through the blade airfoil. In the finished blade, therefore, the platinum pin faces are exposed, flush with the exterior airfoil surfaces. At the end of a service interval, blades are typically stripped and re-coated. The platinum pins have to be masked during the stripping process to prevent chemical attack on the platinum. If the pins are not precisely masked, the stripping chemical will melt the pins, leaving minute holes in the airfoil surfaces. This leads to a problem known as “repair fallout” with as many as 25% of blades being disposed of rather than recoated.